An air-mass trajectory study of the transport of radioactivity from Fukushima to Thessaloniki, Greece and Milan, Italy

Analyses of I-131, Cs-137 and Cs-134 in airborne aerosols were carried out in daily samples at two different sites of investigation: Thessaloniki, Greece (40 degrees N) and Milan, Italy (45 degrees N) after the Fulcushima accident during the period of March-April, 2011. The radionuclide concentrations were determined and studied as a function of time. The I-131 concentration in air over Milan and Thessaloniki peaked on April 3-4, 2011, with observed activities 467 mu Bq m(-3) and 497 mu Bq m(-3), respectively. The Cs-134/Cs-137 activity ratio values in air were around 1 in both regions, related to the burn-up history of the damaged nuclear fuel of the destroyed nuclear reactor. The high I-131/Cs-137 ratio, observed during the first days after the accident, followed by lower values during the following days, reflects not only the initial release ratio but also the different volatility, attachment and removal of the two isotopes during transportation due to their different physico-chemical properties. No artificial radionuclides could be detected in air after April 28, 2011 in both regions of investigation. The different maxima of airborne I-131 and (134),Cs-137 in these two regions were related to long-range air mass transport from Japan, across the Pacific and to Central Europe. Analysis of backward trajectories was used to confirm the arrival of artificial radionuclides following atmospheric transport and processing. HYSPLIT backward trajectories were applied for the interpretation of activity variations of measured radionuclides. (C) 2013 Elsevier Ltd. All rights reserved.